In recent years, an apparatus for measuring eye movement has received attention. If the eye movement can be measured, such technology is applied to a vision field test or a fundus tomographic image acquiring apparatus for obtaining a higher resolution image, and hence a more accurate fundus test can be performed.
In order to measure the eye movement, there are various methods such as a corneal reflex method (Purkinje image) and a search coil method. Among others, a method of measuring eye movement from a fundus image is being studied, which is simple and imposes little load on a subject.
In order to measure eye movement accurately using a fundus image, it is necessary to extract a characteristic point from the fundus image, to search for and detect a characteristic point in the image to be processed, and then to calculate a movement amount of the characteristic point. These steps need to be processed at high speed. The step of extracting the characteristic point is important from a viewpoint of measurement stability, accuracy, and reproducibility of eye movement. As the characteristic point of the fundus image, a macula lutea, an optic papilla (hereinafter referred to as papilla), or the like is used. Because an affected eye or the like has an incomplete macula lutea or papilla in many cases, a blood vessel may be used as the characteristic point of the fundus image. A method of extracting a characteristic point of a blood vessel is disclosed in Patent Literature 1.